Table of Contents
Advertisement
Time of Service
New
Start of Service
ntermediate Service to The coloring changes to brown or black with distributed small silvery white areas.
End of Service Life
valleys
Fig. 39 Normal Service Wear
Contact Appearance
Curling and Separation
of Corner of Contact
Irregular Contour or
Slantwise Wear
tacts.
ing direct
Large Beads of Silver
On Edges of Contacts
Welded Spot (Core of
Smooth, Shining Silver
Surrounded by a
Roughened Halo)
I.B. 8926-1
CONTACT EVALUATION
Contact Appearance
The new contact has a uniform silver color.
The contact surface will have a blue coloring. The geometric form of the contact is unchanged.
The sharp outer corners will be rounded with small silver beads. (See Figure 39.)
The surface has a finely chiselled appearance. Material transfer causes small peaks and
in the contact button surface. (See Figure 40.)
ABNORMAL WEAR CONDITIONS
Cause
Curling is usually a result of service that produces very high heat,
as under jogging or inching duty.
One corner of a contact may wear more quickly than the other three
corners. This wear is normally due to misalignment of the moving and stationary con-
Contacts should be replaced if it is apparent that one contact is nearly mak-
contact with the contact carrier.
Breaking an excessive current.
Making an excessive current. High frequency of operation, i.e., jogging.
Fig. 40 End of Service Life
- Page 28 -
Hide quick links:
Advertisement
Table of Contents
